Mysteries of the brain

A man partially recovers from 19 years in a minimally conscious state, and …

I've said it before, I'll say it again: brains are strange things. The fact that we, as humans, have comparatively large and complex brains accounts for our dominance on the planet, our language, technology and all the other things that make it possible for me to sit in front of my powerbook and write this column, and for you to read it. But there's much that happens within our skulls that we don't fully understand yet, and by and large brains are fragile things. It doesn't take much to stop one working–a few minutes without oxygen is enough to destroy a brain.

There is a common assumption that brains are also not very good at repairing themselves. By and large this is true. Unlike the liver, which has an enormous capacity for self-repair, neurons that die are often never replaced, making spinal cord or traumatic brain injuries permanent conditions. But not always. Such is the remarkable case of Terry Wallis, who suffered a traumatic brain injury that left him in a minimally conscious state (MCS) for 19 years.

Over this time, Terry's brain slowly rewired itself in a way that has not been observed before, and Terry emerged from his MCS able to speak and with a limited ability for movement that has since improved. It must be stressed that the Hollywood image of a man waking from a coma and taking up where he left off could not be further from reality in Terry's case. Despite regaining the power of speech, Terry is still disabled following his brain injury.

Over the course of his recovery, doctors used a new imaging technique called diffusion tensor imaging (DTI) to follow the way his brain rewired itself, and compared it to an MCS patient showing no signs of recovery. The findings are published in the Journal of Clinical Investigation, along with a commentary. Terry's accident severed a lot of neuronal connections between different brain areas. The growth of new axons reconnected these areas, but in doing so created pathways and structures never normally seen in brains.

I imagine that these findings are going to be seized upon by bioconservatives to support their position over the sad affair of Terri Schaivo, but the only similarities between these cases are the patients' first names. Terri Schiavo suffered from a persistent vegetative state (PVS), a different condition to MCS, where patients experience infrequent but real periods of conciousness. Terri's case was reviewed time and time again, and each diagnosis confirmed the PVS, as did her autopsy. Recovery from MCS remains rare, especially after more than 12 months. Terri Schiavo had lost most of her cerebral cortex, a much more severe injury than that of Terry Walker.

Another neuro-related news item caught my eye the other day, and it serves to reinforce my original point. Natives of the British Isles will be familiar with the Geordie accent - I'm not sure if I can think of any Geordies that might be well known to US readers, but suffice to say those who hail from Newcastle have a rather distinctive way of speaking. This was true for one Linda Walker, up until she she suffered a stroke at the age of 60. Following the stroke, Linda's Geordie lilt was gone, to be replaced by a Jamaican accent. Strange as it sounds, there have been around 50 cases recorded of foreign accent syndrome, which results from damage to the speech centers of the brain.